Overweight is related to several cancers, CVD, and NIDDM, and the prevalence of overweight is increasing rapidly (NIH 1998). This study will develop and then evaluate in a randomized controlled trial a cell phone and web-based application (mDIET) that can be used as an assessment and intervention tool to improve dietary behaviors in overweight and moderately obese women age 25 through 55 years. Forty women will be randomized to the mDIET group or a control group. The mDIET (Mobile Diet Intervention through Electronic Technology) system will include a web-application that shares data and communicates via a server with the cell phone. mDiet will identify unique dietary needs for each participant through an initial assessment focusing on most frequently eaten foods (including fast food) and eating behaviors that may lead to ncreased caloric intake (e.g., food preparation techniques, snacking while watching tv). An expert system will use logic rules to filter this information and create concrete goals to target. These goals are then presented to the user via the cell phone on a daily basis to serve as a prompt for food selection and behavioral improvements. The study will examine whether real-time communication to "pull" information rom users and "push" appropriate intervention messages at critical point-of-decision moments will translate into greater goal attainment and dietary improvement. The control group will participate in the same baseline dietary assessment and will receive feedback on their assessment via print materials. The primary outcome will be the effect of the mDIET system on BMI at 4 months. This study will help determine whether this novel combined use of web assessment and cell phone technology can improve the effectiveness of dietary interventions by facilitating self-monitoring, increasing awareness of behaviors, and providing appropriate prompts at critical decision time-points. If the mDIET system is successful, it will be incorporated into a larger R01 study focused on obesity management utilizing cell-phone technologies.